Mitogen-induced membrane changes and cell proliferation in T lymphocyte subpopulations.

Rabbit thymus-dependent lymphocytes were exposed to phytohemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) or anti-immunoglobulin at various stages of maturation. Proliferation (induction of DNA synthesis) and early membrane events (turnover of membrane phospholipids) were measured in neonatal thymocytes, normal adult thymocytes, prednisolone-resistant thymocytes and lymph node lymphocytes. In immature thymocytes PHA induced only a marginal increase in DNA synthesis. The mitotic response increased with maturation, but only peripheral T lymphocytes exhibited maximum stimulation. Con A and PWM were able to induce DNA synthesis in immature thymocytes and the degree of stimulation was shown to increase with maturation. In contrast to the different degree of proliferation of thymocytes induced by PHA or Con A the incorporation of [14C]oleate, [14C]choline or [14C]acetate into phospholipids was stimulated to the same degree by these lectins. Reactivity of T lymphocytes, as measured by early membrane changes at different stages of maturation, to different T cell mitogens appears to be identical. Differences in degree of cell proliferation therefore may be secondary phenomena due, in part, to tissue culture conditions. Reactivity to mitogens as measured by phospholipid turnover appears to be an early acquired function in the maturation of lymphocytes of the T cell line.